Random section and random simplex inequality
A. E. Litvakab,
D. N. Zaporozhetsc a Dept. of Math. and Stat. Sciences, University of Alberta, Edmonton, AB, Canada, T6G 2G1
b Saint Petersburg State University
c St. Petersburg Department of Steklov Mathematical Institute of Russian Academy of Sciences
Abstract:
Consider some convex body
$K\subset\mathbb R^d$. Let
$X_1,\dots, X_k$, where
$k\leq d$, be random points independently and uniformly chosen in
$K$, and let
$\xi_k$ be a uniformly distributed random linear
$k$-plane. We show that for
$p\geq -d+k+1$,
$$
\mathbf E |K\cap\xi_k|^{d+p}\leq c_{d,k,p}\cdot|K|^k \mathbf E |\mathrm{conv}(0,X_1,\dots,X_k)|^p,
$$
where
$|\cdot|$ and
$\mathrm{conv}$ denote the volume of correspondent dimension and the convex hull. The constant
$c_{d,k,p}$ is such that for
$k>1$ the equality holds if and only if
$K$ is an ellipsoid centered at the origin, and for
$k=1$ the inequality turns to equality.
If
$p=0$, then the inequality reduces to the Busemann intersection inequality, and if
$k=d$ – to the Busemann random simplex inequality.
We also present an affine version if this inequality which similarly generalizes the Schneider inequality and the Blaschke-Grömer inequality.
Key words and phrases:
Blaschke-Grömer inequality, Blaschke-Petkantschin formula, Busemann intersection inequality, Busemann random simplex inequality, convex hull, expected volume, Furstenberg-Tzkoni formula, random section, Schneider inequality.
UDC:
519.2 Received: 11.11.2021